On 06/26/2012 01:12 PM, David Rientjes wrote:

On Mon, 25 Jun 2012, Glauber Costa wrote:

quoted

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 83e7ba9..22479eb 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h

@@ -21,6 +21,7 @@
  #define _LINUX_MEMCONTROL_H
  #include <linux/cgroup.h>
  #include <linux/vm_event_item.h>
+#include <linux/hardirq.h>

  struct mem_cgroup;
  struct page_cgroup;

@@ -409,6 +410,12 @@ struct sock;
  #ifdef CONFIG_CGROUP_MEM_RES_CTLR_KMEM
  void sock_update_memcg(struct sock *sk);
  void sock_release_memcg(struct sock *sk);
+
+#define mem_cgroup_kmem_on 1
+bool __mem_cgroup_new_kmem_page(gfp_t gfp, void *handle, int order);
+void __mem_cgroup_commit_kmem_page(struct page *page, void *handle, int order);
+void __mem_cgroup_free_kmem_page(struct page *page, int order);
+#define is_kmem_tracked_alloc (gfp & __GFP_KMEMCG)
  #else
  static inline void sock_update_memcg(struct sock *sk)
  {

@@ -416,6 +423,43 @@ static inline void sock_update_memcg(struct sock *sk)
  static inline void sock_release_memcg(struct sock *sk)
  {
  }
+
+#define mem_cgroup_kmem_on 0
+#define __mem_cgroup_new_kmem_page(a, b, c) false
+#define __mem_cgroup_free_kmem_page(a,b )
+#define __mem_cgroup_commit_kmem_page(a, b, c)
+#define is_kmem_tracked_alloc (false)
  #endif /* CONFIG_CGROUP_MEM_RES_CTLR_KMEM */
+
+static __always_inline
+bool mem_cgroup_new_kmem_page(gfp_t gfp, void *handle, int order)
+{
+	if (!mem_cgroup_kmem_on)
+		return true;
+	if (!is_kmem_tracked_alloc)
+		return true;
+	if (!current->mm)
+		return true;
+	if (in_interrupt())
+		return true;

You can't test for current->mm in irq context, so you need to check for
in_interrupt() first.

 >
Right, thanks.

Also, what prevents __mem_cgroup_new_kmem_page()
from being called for a kthread that has called use_mm() before
unuse_mm()?

Nothing, but I also don't see how to prevent that.
At a first glance, it seems fair to me to say that if a kernel thread 
uses the mm of a process, it poses as this process for any accounting 
purpose.